Risk of race condition in non-atomic file operation RB-E1002

Non-atomic file operations can cause problems that are difficult to reproduce, especially in cases of frequent file operations in parallel, such as test runs with parallel_rspec.

For example, creating a directory if there is none, has the following problems:

An exception occurs when the directory didn’t exist at the time of exist?, but someone else created it before mkdir was executed.

Bad practice

# race condition with another process may result in an error in `mkdir`
unless Dir.exist?(path)
  FileUtils.mkdir(path)
end

# race condition with another process may result in an error in `remove`
if File.exist?(path)
  FileUtils.remove(path)
end

Recommended

# atomic and idempotent creation
FileUtils.mkdir_p(path)

# atomic and idempotent removal
FileUtils.rm_f(path)